Field of Invention
The present invention relates to a lead frame structure, and more particularly, to a lead frame structure for a quad flat no-lead (QFN) package.
Description of Related Arts
Please refer to FIG. 1. FIG. 1 is a flowchart 100 showing a method for forming a lead frame structure of the prior art. As shown in FIG. 1, elements of a lead frame are first formed in step 110. And in step 120, some portions of the lead frame are half etched to reduce thickness partially. Thereafter, a metal layer is plated on the lead frame for enhance electrical connection in step 130.
Please refer to FIG. 2, and refer to FIG. 1 as well. FIG. 2 is a cross-sectional view of the lead frame structure 20 of the prior art. As shown in FIG. 2, since the metal layer 230 is plated on the lead frame 200 after formation of the elements 210, 220 of the lead frame 200, some residual metal material 240 may be left on side walls of the elements 210, 220 of the lead frame 200, such that the package material will delaminate from the metal layer 230 of the lead frame 200 with the residual metal material 240, so as to debase the electrical reliability since moisture will invade the package from the chink of the delaminated parts. Therefore, after the lead frame structure 20 being encapsulated, the lead frame structure 20 is weakly bonded with the package material due to the residual metal material 240.